Present supplemental restraints including deployable knee bolsters and air bags are used in motor vehicles to provide occupant protection by providing a reaction element that resists the motion of an occupant in a controlled manner during an impact. Airbags are inflatable and are commonly used to provide increased occupant protection for the torso and head. Knee bolsters are deployed to help resist forward movement of the knees and thighs. Knee bolsters can also be inflatable, but commonly include molded plastic bladders and when fully deployed occupy much less volumetric space than an airbag. Some present knee bolsters reposition a vehicle trim component into a knee area of a passenger compartment upon detection of a collision. Once deployed, present supplemental restraints, especially inflatable supplemental restraints, need to be replaced and associated interior trim components may also need to be replaced. Present supplemental restraints are controlled by and selectively activated by an electronic control unit that receives signals from sensors, and processes such signals using software control logic stored in the electronic control unit. The electronic control unit sends out command signals to the supplemental restraints responsive to the signals received and the control logic.
The availability of supplemental restraints and the deployment control command logic each vary with seating position. Present logic tries to determine whether or not there is a passenger in the front passenger (non-driver) seat, and whether the passenger is a light weight passenger, such as a child or a small adult. If the passenger is characterized as a light weight passenger, for example lighter than a fifth percentile female, a supplemental restraint may, depending on the capabilities of the supplemental restraint, be not deployed, or be deployed with less force, or be deployed with a reduced inflation shape mode. Deployment of a supplemental restraint associated with a seat position is not undertaken if it is believed that that seat position is not occupied, or if the occupant is perceived as too small.
For a front passenger seating location, present safety restraint system uses an occupant classification sensor to deactivate both supplemental and active restraint components (front airbags, side air bags, pretensioners, etc.) both when there is no occupant in a seat and when an occupant is perceived by the system as being smaller than a predetermined threshold, such as smaller than a 5th percentile female. Such deactivation is done to both keep the airbags from deploying when the seat is empty to avoid an unnecessary deployment and the expense associated with replacing the used restraints, and when the seat is occupied by small children including babies in car seats to avoid injury to the children who may be injured by the force of the deploying airbag. While deployment of a knee bolster is very unlikely to injure a child in a child seat, as the child is likely to be out of the range of a deployed knee bolster, it is still advantageous to inhibit deployment when the seat is empty or contains a child seat to avoid the unnecessary expense of an ineffective deployment. However, for children large enough to have legs that reach into the passenger foot well area, the active knee bolster can improve the kinematics protection of a small occupant or a large child whose legs are in the passenger foot well area. The protection afforded by the knee bolster beneficial independent of whether or not the passenger airbag is deployed.
Possible changes in vehicle interiors, including front seats rotatable to rear facing positions as may be enabled by autonomous vehicles, and increased supplemental restraints in rear seats, are rendering current sensing systems and deployment logic inadequate for future vehicle configurations. It is desirable to provide improved occupant sensors and improved supplemental restraint deployment control command logic suited for used with future vehicle configurations.